Refrigeration apparatus with hot gas defrost



REFRIGERATION APPARATUS WITH HOT GAS DEFROST Filed D60- 1, 1959 FIG].

Oct. 24, 1961 L. B. M. BUCHANAN 2 Sheets-Sheet 1 EVA =ORATOR INVENTORCONDEN SER FIGZ.

H H LESLIE B.M.BUCHANAN Mag/ ATTO R N EY al 8 5 2 h I.

REFRIGERATION APPARATUS WITH HOT GAS DEFROST Filed Dec. 1, 1959 Oct. 24,1961 a. M. BUCHANAN 2 Sheets-Sheet 2 INVEN TOR LESLIE B. M. BUCHANANATTORNEY 3,005,319 REFRIGERATION APPARATUS WITH HOT GAS DEFROST LeslieB. M. Buchanan, Galloway, Ohio, assignor to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of Pennsylvania FiledDec. 1, 1959, Ser. No. 856,566

7 Claims. (Cl. 62-156) This invention relates to refrigeration apparatusand more particularly to an improved control system for socalled hotgas, or bypass, defrosting systems.

More particularly, this invention concerns an improved arrangement andcontrol system for a valve which alter natively permits compressedrefrigerant to flow through a restrictor into a refrigerant evaporatoror to bypass the restrictor and flow directly into the evaporator foreffecting, respectively, refrigeration or defrosting of the evaporator.In accordance with this invention, actuation of the defrost valve toinitiate defrosting and subsequent actuation thereof to terminatedefrosting is effected autnited States atent O matically in response toconditions of operation of the refrigerator employing the refrigerationsystem.

This invention constitutes an improvement upon the defrost valvearrangement and control described and claimed in my Patent No.2,957,316, issued October 25, 1960, entitled Refrigerating ApparatusWith Hot Gas Defrost Means, and assigned to the same assignee as thisinvention.

' The principal object of this invention is reliable and accuratecontrol of defrosting for a refrigeration system, which objective isachieved through the use of a relatively simple, inexpensive valve andcontrol mechanism capable of reliable performance. over an extendedperiod of time.

In accordance with this invention a unitary selfactuating hot gas bypassvalve is so disposed in the refrigerant circuit that there is a flow ofwarm refrigerant through the body of the valve during both refrigeratingand defrosting operations. By this arrangement, heat from the warmrefrigerant maintains the components of the valve at a sufiicientlyelevated temperature to preclude condensation of moisture on the exposedsurfaces thereof even though portion of the valve may be subjected to acooling effect from low pressure, vaporizable refrigerant fiuid.Moreover, the valve is so connected into the refrigerant circuit thatits automatic self-closing function is performed in response to pressureconditions existing at or near the outlet of the evaporator. Thisfeature of the improved valve gives more reliable defrost termination;first, because the valve responds to the condition of that portion ofthe evaporator which is last to defrost and, second, the pressureresponsive portion of the valve is not subjected to the initial inrushof high pressure refrigerant to the evaporator at the inception of thedefrost operation, which cause premature termination of defrosting withsome prior defrost controls. Also, sensing the pressure at the outletend of the evaporator eliminates the eifect of pressure drop through theevaporator. This varies with different evaporators, and differentcompressor pumping rates.

Another novel feature of the improved defrost control of this inventionresides in the mechanism provided for automatically actuating the bypassvalve to open position to initiate defrosting in response totheoccurrence of a predetermined number of refrigerator operations.Specifically, the problem solved by this invention is the provision of areliable mechanism for opening the defrost valve and immediatelythereafter freeing the movable portion of the valve for automaticclosing at the termination of the defrost operation.

The control of this invention also includes a temperature responsivecompensating feature which assures reliable operation of the controlunder conditions of unusually low, and unusually high, ambienttemperature.

Other objects, advantages and features of the invention will be madeapparent by the following detailed description which refers to theaccompanying drawings wherein:

FIG. 1 is a perspective view of a domestic refrigerator adapted toemploy this invention;

FIG. 2 is an enlarged sectional view of the improved defrost control ofthis invention together with a schematic illustration of therefrigerating circuit with which it is used;

FIG. 3 is a sectional view of the defrost control taken generally asindicated by the line -IHIII in FIG. 2;

' FIG. 4 is a diagrammatic view of the defrost control illustrating avalve opening operation of the control; and

FIG. 5 is a fragmentary perspective view of the valve actuatingmechanism of the control.

Referring to FIG. 2 in detail, the improved defrost control of thisinvention is identified generally by the reference numeral 11 and isparticularly adapted for use in a compressor-condenser-evaporatorrefrigeration systern. The system illustrated includes amotor-compressor unit 12 for compressing vaporous refrigerant which iscondensed in a condenser 13 and conveyed through a restrictor device 14into a low pressure evaporator or cooling unit 15, wherein therefrigerant is vaporized to absorb heat. Vaporous refrigerant isreturned to the inlet of the motor-compressor unit 1'2 through a suctionconduit 16. Similar conduit means are employed to serially connect themotor-compressor unit 12, the condenser 13, the restrictor 14 and theevaporator 15. Refrigerating systems of this type are frequentlyemployed to refrigerate food storage compartments of domesticrefrigerators, such as that illustrated in FIG. 1. The evaporator 15 ofthe circuit may be disposed within a compartment 17 of the refrigeratorfor absorbing heat therefrom and the condenser 13 of the circuitdisposed exteriorly of the compartment for dissipating heat to airambient the refrigerator.

In a hot gas, or bypass, type defrostable refrigerating system, withwhich this invent-ion is concerned, there is provided a bypass line orconduit 18 for conveying compressed refrigerant directly to theevaporator 15, bypassing the restrictor 14. Warm vaporous refrigerantconveyed to the evaporator 15 by this line adds heat to the evaporatorto effect removal of ice and frost which collects thereon. Control ofthe flow of refrigerant fluid through the bypass conduit 18 is exercisedby a valve, indicated generally at 19, forming a part of the defrostcontrol 11. This valve is disposed in the conduit means connectingthe'discharge outlet of the motor-compressor unit 12 and the restrictor14 and, preferably, upstream of the condenser 13 in the conduit carryinghot discharge gas from the motor-compressor 12.

The defrost control valve 19 includes a body 21 formed of metal or othergood heat conducting material which contains refrigerant flow passages22 and 22a that provide an inlet 23 and two outlets 24- and 25 for thevalve. Disposed within the valve body 21 for movement in the flowpassages 22 is a valve member 26 which cooperates with a seat 27 forestablishing or disestablishing refrigerant flow through valve outlet 25communicating with the bypass conduit 18. When the valve member 26 in inits closed position as shown in FIG. 2 (i.e., seated against seat 27),refrigerant entering the valve body 21 is prevented from flowing intothe bypass conduit 18 and is constrained to flow through outlet 24 tothe condenser 13 and subsequently to the restrictor 14. The valve member25 is movable to an open position (illustrated in FIG. 4) in which it isdisplaced from its seat 27, whereby refrigerant is permitted to flowinto the bypass conduit 18.

It is to be noted that regardless of the condition of the defrostcontrol valve 19, warm refrigerant is conveyed through the passages ofthe valve body 21 whenever the motor-compressor 12 is operated. Heatimparted to the valve body 21 is conducted to other elements of thecontrol valve to warm these elements and prevent condensation ofmoisture from the ambient air thereon. As is explained in greater detailbelow, this warming effect is particularly beneficial with regard toprolonging the life of the defrost termination means of the valve, whichincludes a pressure responsive device in the form of a bellows 28 whichis brazed, or otherwise secured, in fluidtight relationship, to thevalve body 21. Expansion of the bellows 28 in response to an increase influid pressure within the evaporator of the refrigerating system isemployed to actuate valve member 26 to its closed position to terminatedefrosting. For this purpose, the interior of the bellows 28 in iscommunication with a portion of the refrigerant circuit through apassage 29 in the valve body 21 and a pressure line 3-1 having one endsecured to the valve body and opening into passage 29 and having itsother end in communication with a portion of the suction conduit 16,preferably near the outlet of the evaporator, as indicated at 32 in FIG.2.

Movement of an end wall portion 33 of bellows 28 is transmitted to themovable valve member 26 by means of a valve stem 34, which has afluid-tight connection with the bellows wall 33 and is affixed to thevalve member 26. The stem 34 slides in an elongated bore provided in asleeve portion 36 of the valve body 21. As can be readily appreciated, aclose fit is provided between stem 34 and the sleeve 36 to minimizeleakage of refrigerant vapor from valve passage 22 into the interior ofthe pressure responsive bellows 28. It will be noted, however, that theinterior of the bellows 28 is in communication with a portion of therefrigerant circuit which is operating at a lower pressure than therefrigerant flowing through valve passages 22 and that any refrigerantleaking into the bellows 23 will be carried away through pressure line31.

It is to be expected that a small quantity of higher pressurerefrigerant will leak by valve member 26 during refrigerating operationin spite of efforts to provide for tight seating of valve member 26against its seat 27. Ex pansion of such refrigerant in valve passage22a, of course, refrigerates the valve body 21 and by conduct-ion coolsthe bellows 28. Under some conditions, this might tend to promotecondensation of water on the body of the valve and on the bellows. Thiscould have a detrimental effect on the life of the control valve. Thiscondition is obviated by the refrigerant flow arrangement of thisinvention because, as mentioned previously, during all operating periodsof the system warm refrigerant is conveyed through the valve body 21.The latter, being constructed of good heat conducting material, conveysheat from the Warm refrigerant to the bellows and other portions of thevalve to keep the temperature of these elements sufiiciently high topreclude the condensation of moisture thereon.

The valve member 26 is moved to its closed position to terminatedefrosting when the bellows 28 senses the existence of a pressurecondition at the outlet of the evaporator 15 which indicates that thetemperature of the evaporator has risen to some value above 32 F., sothat all frost and ice has been melted therefrom. The jointure ofpressure line 31 connecting bellows 28 into the refrigerant circuit atpoint 32 near the outlet of the evaporator 15 is desirable for reliabledefrost termination. The exit end of the evaporator, generally, is thelast portion of the evaporator to defrost and the sensing of evaporatorpressure for defrost termination purposes should, therefore, be done atthis point. This connection location also minimizes the pressure surgeto which the defrost termination bellows 28 is subjected at thebeginning of a defrosting operation. It can readily be appreciated thatthe surge of high pressure refrigerant into evaporator 15 immediatelyfollowing opening of defrost valve 19 will be damped, or dissipated, inthe passages of the evaporator and premature closing of valve 19 as aresult of this pressure surge will be avoided.

The pressure at which the bellows 28 effects closing of the valve member26 is determined by restraining means forming a part of the control 11and adapted to restrain movement of the valve stem 32 until thepredetermined pressure occurs. This restraining means preferably takesthe form illustrated in the drawings and includes a lever 37, which ispivotally mounted on a pin 38 and has an intermediate portion thereofbearing against an exposed end portion 39 of the valve stem 34. The endof the lever -37 opposite pin 38 carries a roller 40 which is adapted tobe engaged and restrained by a detent spring member 41 when the lever 37occu-. pies a raised position in which it elevates the valve stem 34 andlifts valve member 26 from its seat 27. This condition is illustrated inFIG. 4, from which it will be noted that the roller 40, and consequentlythe lever 37, are restrained against downward, or counterclockwise,movement by an offset finger 42 formed in the lower end portion of thedetent spring 41. The holding force or effect of the detent spring 41 isovercome when suffia cient pressure exists within the bellows 28 toapply force through the valve stem 34 to the lever 37 to cause theroller 40 to push the detent spring 41 to the right and ride over thefinger 42 on that spring.

The optimum defrost termination pressure may vary from one refrigerationsystem to another and it is, therefore, desirable to provide means foradjusting the restraining force ofiered by the detent spring 41. In thepreferred embodiment illustrated, this adjustment is made possible bythe manner of mounting the detent spring 41 within the control 11. Asbest shown in FIGS. 2 and 3, the spring 41 is pivotally carried on afulcrum 43 formed in the control casing. The end of the spring oppositethe finger 42 bears against an adjusting screw 44, also mounted in thecontrol casing. For the arrangement illustrated in FIG. 2, turningadjusting screw 44 to move it downwardly increases the clockwise biasingforce of the spring 41 to increase the pressure required in bellows 28to cause the roller 40 to ride over the spring detent finger 42.Conversely, turning adjusting screw 44 to move it upwardly decreases thebias afforded by spring 41 and, consequently, decreases the value of thedefrost termination pressure in bellows 28.

It is also recognized that the optimum defrost termination pressure mayvary with changes in ambient temperature. Under high ambient temperatureconditions, the quantity of heat which is available from themotorcompressor unit 12 to warm refrigerant being pumped to theevaporator 15 during defrosting is higher than under average temperatureconditions, with the result that that portion of the evaporator throughwhich refrigerant flows is rapidly elevated in temperature. Other, moreremote, portions of the evaporator structure and other frost coveredportions of the refrigerator may lag behind the refrigerant carryingportion and actually still have frost or ice remaining thereon when thepressure of the refrigerant in the refrigerant carrying portions of theevaporator rises to the value for which the defrost control valve 19 isset to close. To overcome this problem it is desirable to increase theperiod of defrost during high ambient temperature conditions to providesufficient time for the most remote portions of the evaporator todefrost. This can be accomplished by raising the pressure value at whichthe defrost control is set to close.

A different condition exists under extremely low ambient temperatureconditions, of the order of =60 F. and below. In low room temperaturesan increasing quantity of refrigerant in the system is absorbed in thebody of lubricating oil contained in the motor-compressor unit 12 and,in part, circulating through the refrigerating system. The resultingdecrease in the quantity of refrigerant being circulated through thesystem limits the maximum pressure which may occur in the evaporator.Under extreme conditions, this maximum pressure may be less than thatpressure which is required to close the defrost control valve underaverage operating conditions. It is, therefore, desirable to lower thepressure setting of the defrost control valve under extremely lowambient conditions to provide insurance against'the possibility of thepressure in the evaporator never reaching defrost termination pressure.

. In accordance with this invention, the defrost control includes meansfor respectively increasing or decreasing the restraining force actingin opposition to the valve closing forces from the bellows 28 inaccordance with a rise or a fall in ambient temperature. In the firstplace, the defrost control 11 is preferably located in the vicinity ofthe motor-compressor unit so as to be subjected to substantially thesame temperature conditions as the motor-compressor. In addition, thedetent spring 41 of the restraining means is formed of a bimetallicstrip to provide automatic variation of the force characteristics of thespring with changes in ambient temperature. In the embodiment. of theinvention illustrated in FIGS. 2 and 3, the more active material of thebimetallic spring 41 is located on the back face of the spring 41 (Le,to the right as the spring is viewed in FIG. 2). Thus, an increase inambient temperature prompts the spring 41 to deflect to the left (asviewed in FIG. 2) to increase the restraining force applied to theroller 40 by the spring finger 42; Conversely, a decrease in ambienttemperature causes the spring 41 to tend to move to the right relievingin part the restraining force offered to the roller 40. Because therestraining force imposed on roller 40 is transmitted to the bellows 28through the lever 37 and the valve stem 34, the bias of spring 42directly determines the pressure required to be sensed by the bellows 28in order to close valve 19 and effect termination of a defrostingoperation.

Any suitable provision may be made for initiating a defrost operation bymoving the valve control lever 37 from the position shown in FIG. 2 tothe position shown in FIG. 4. For example, this may be accomplishedmanually by the user of the refrigerator. However, in accordance withthis invention, it is preferable that initiation of the defrostingoperation take place in response to certain conditions of operation ofthe refrigerator in which the system is employed. In the illustratedapparatus, means are provided for initiating defrosting when therefrigerator door has been opened and closed a predeterminednumber oftimes. As has been previously known, the accumulation of frost and iceon the evaporator of a domestic refrigerator is related to opening andclosing of the refrigerator door.

Referring to FIG. 1, the refrigerator cabinet is provided with a plunger46 which projects from the front of the cabinet and is en-gageable by aportion of the cabinet door 50 when the door is moved to closedposition. This plunger 46 forms a part of the defrost control 11 and isan extension of a slider 47 (see FIGS. 2 and 3) mounted forreciprocating movement in the control casing. Each time the refrigeratordoor 50 is closed it engages plunger 46 and moves slider 47 to the left,as viewed in FIG. 2. Rightward movement of the slider 47 and extensionof plunger 46 when the refrigerator door is opened is effected by aspring 48.

- Reciprocations of the slider 47 are reflected in rotary movement of aratchet wheel 49 having a plurality of teeth 51 on the peripherythereof, presenting an annular series of drivensurfaces which areengageable by a spring pawl 52 carried by slider 47. The majority of thepawl teeth 51 have the same configuration and the driven surfaces theypresent to the pawl 52 are uniformly spaced about the periphery of theratchet wheel, thus enabling the pawl 52 to effect equal increments ofrotation of the wheel 49 for most of the reciprocating movements of theslider 47. One region of the ratchet wheel 49, however, is provided withan enlarged tooth 53 adapted to cause a large increment of rotation ofthe wheel 49 for one reciprocation of the slider 47, the purpose ofwhich is explained hereinafter. This is accomplished because the drivensurface of tooth 53 presented to the pawl 52 isv spaced a greaterperipheral distance from the driven surface of the tooth 51 preceding itin the direction of wheel movement than the uniform distance betweenadjacent teeth 51.

Mounted on the ratchet wheel 49 for rotation therewith are a pair of camsurfaces 54 and 55 having follower surfaces engageable, respectively,with a valve actuating arm 56 and a return arm 57. The follower surfaceof cam 54 is substantially cylindrical except for a small arcuateportion thereof which contains a cutout 58 adapted to loosely receive afollower shoe 59 carried by actuating arm 56. Cam 54 is adapted torestrain movement of the valve actuating arm 56 against the bias of anactuating spring 61 connected to the arm 56 and to release the actuatingarm at that point in its rotary movement at which the follower shoe 59is aligned with cutout 58. It can be seen that when the shoe 59 isaligned with cutout 58 the actuating arm 56 is free to move clockwiseabout a pivot pin 60 so that a finger 62 projecting from the end ofactuating arm 56 engages lever 37 and moves it to open the defrostcontrol valve 19. Actuating arm 56 is released once in each revolutionof cam 54 to initiate a defrosting operation. The number of dooropenings required to rotate cam 54 through a complete revolution isdetermined by the number of teeth on the ratchet wheel 49. It has beendetermined that satisfactory operation can be obtained by initiatingdefrosting each time the refrigerator door has been opened and closedtwenty-nine times, so approximately twenty-nine teeth may be provided onratchet wheel 49.

Return arm 57 of the valve operating mechanism is employed to returnactuating arm 56 to the position shown in FIG. 2 to free valve lever 37from the influence of the actuating arm 56 immediately after valve 19has been opened. The'follower surface on cam 55, which controls movementof return arm 57, has a spiral configuration with its high pointterminating in an abrupt cutoff 63. When cam 55 is rotated to the pointat which the cutoff 63 is moved beyond the end of return arm 57 a returnspring 64 connected to return arm 57 rotates the latter counterclockwiseabout the pivot pin 60 and a portion of arm 57 engages a finger 66 onactuating arm- 56 and moves arm'56 away from the valve lever 37. Inorder for this operation to take place it is necessary that returnspring 64 apply a greater turning moment to return arm 57 than isapplied to actuating arm 56 by actuating spring 61.

The angular position relationship between the cutout 58 of cam 54 andthe cutofl? 63 of cam 55 is such that the release of actuating arm 56 iseffected prior tothe release of return arm 57 but only a small incrementof rotation of the ratchet wheel 49 separates release of the two arms 56and 57. The object of this arrangement is to enable the release ofactuating arm 56 and its return, through release of the return arm 57,to be eifected in that increment of rotation of the ratchet wheel 49which can be effected by a single reciprocation of the slider 47.Certain manufacturing tolerances must, of course, be permitted withrespect to the relative locations of the cam cutout58 and the cam cutofi63 as well as in the configuration of those portions of arms 56 and 57which are engaged by earns 54 and 55. A definite increment of rotation,say on the order of 5 degrees, should be provided in the camming systembetween the release of arms 56 and 57 to prevent premature release ofthe return arm 57, which malfunction prevents opening the defrost valve19 at the desired time. It is necessary, therefore, that ratchet wheel49 be rotated a sufiicient amount to insure the release of the returnarm 57 after the release of actuating arm 56. In accordance with thisinvention, the ratchet wheel 49 is caused to undergo a larger incre- 7ment of rotation at that increment in its rotation in which the arms 56;and 57 are released. This increased increment of movement is effected bythe enlarged tooth 53 on the ratchet wheel and which is disposed in aregion of the ratchet wheel which is presented to the slider pawl 52 asthe arms 56 and 57 are to be released.

It should be apparent that the extent of movement and path of movementof the slider pawl 52 is such that it will normally pick up the nexttooth on the ratchet wheel 49 whether it be one of the smaller teeth 51or the large tooth 53.

In operation of the improved defrost control valve 19 and the controltherefor, defrosting is initiated when the refrigerator door has beenopened and closed a sufilcient number of times to bring cam cutout 58 inalignment with shoe 59 on actuating arm 56. Movement of actuating arm 56under the action of spring 61 lifts valve actuating lever 37sufficiently to cause the valve member 26 to be lifted from its seat,thereby admitting warm refrigerant directly to the evaporator throughbypass conduit 18. The valve 19 is retained opened by the action ofdetent spring 41 on roller 40 carried by lever 37. Immediately followingrelease of the actuating arm 56 and during the same movement of slider47 caused by closing the refrigerator door, the return arm 57 isreleased to return actuating arm 56 to the position shown in FIG. 2 inorder to permit the defrost control valve 19 to be automatically closedto terminate defrosting. The valve 19 is closed when bellows 28 sensesthe defrost termination pressure at the outlet of the evaporator 15which is suflicient to overcome the restraining force of detent spring41.

Subsequent reciprocations of slider 47, effected by opening and closingof the refrigerator door 50, rotate ratchet wheel 49 and cams 54 and 55counterclockwise as viewed in FIG. 2. The gradual rise on the spiralfollower surface of cam 55 moves return arm 57 in small incrementsagainst the bias of its spring 64. This gradual movement of return arm57 requires relatively light actuating forces on the plunger 46 andslider 47. When cam 55 has been rotated suificiently to commenceclockwise rotation of return arm 57 away from finger 66 on the actuatingarm '56, the cutout in cam 5-4 will have been rotated out of alignmentwith the actuating arm shoe 59, which then comes to rest against thecylindrical surface of cam 54. Movement of the actuating arm 56 in adirection to actuate defrost control valve 19 is thus prevented untilcutout 58 is again aligned with shoe 59.

While the invention has been shown in but one form, it will be obviousto those skilled in the art that it is not so limited, but issusceptible of various changes and modifications without departing fromthe spirit thereof.

What is claimed is:

l. Refrigerating apparatus including a compressor, a condenser, arestrictor, an evaporator, said elements being connected in series flowcircuit in the order named, said compressor having an inlet and anoutlet, valve means connected to said circuit between the outlet of saidcompressor and said restrictor, a bypass conduit providing forrefrigerant flow from said valve means to said evaporator bypassing saidrestrictor, said valve means having a body portion formed of good heatconducting material and having refrigerant flow passages therein, therefrigerant flow circuit between said compressor outlet and saidrestrictor extending through one of the passages in said valve body, avalve member movable to closed and open positions in said passages fordirecting refrigerant respectively to said restn'ctor or to said bypassconduit, means for moving said valve member to its open position, adevice responsive to an increase in suction pressure beyond apredetermined value-for actuating said valve member to its closedposition, said device being carried by said body portion in heattransfer relation therewith, and a pressure line connecting said deviceto said circuit between said evaporator and the inlet of said compressorsubjecting said device to the pressure in said circuit between saidevaporator and said compressor inlet in closing direction of said valvemember.

2. Refrigerating apparatus including a compressor, a condenser, arestrictor, an evaporator, conduit means connecting said elements inseries flow circuit in the order named, said compressor having an inletand an outlet, valve means connected to said conduit means between theoutlet of said compressor and said restrictor, a bypass conduitproviding for refrigerant flow from said valve means to said evaporatorbypassing said restrictor, said valve means having a body portion formedof heat conducting material and having refrigerant flow passagestherein, the refrigerant flow circuit between said compressor outlet andsaid restrictor extending through one of the passages in said valvebody, a valve member movable to closed and open positions in saidpassages for directing refrigerant respectively to said restrictor or tosaid bypass conduit, means for moving said valve member to its openposition, a bellows responsive to an increase in suction pressure beyonda predetermined value carried by said body portion in heat transferrelation therewith for actuating said valve member to its closedposition, and a pressure sensing line connecting said bellows to saidconduit means between said evaporator and the inlet of said compressor,said bellows being subjected to atmospheric pressure in a directionopposite to the closing direction of said valve member and beingsubjected to the pressure in said conduit means between said evaporatorand said compressor inlet in the closing direction of said valve member.

3. Refrigerating apparatus including a compressor, a condenser, arestrictor, an evaporator, conduit means connecting said elements inseries flow circiut in the order named, said compressor having an inletand an outlet, valve means in said circuit between the outlet of saidcompressor and said restrictor, a bypass conduit providing forrefrigerant flow from said valve means to said evaporator and bypassingsaid restrictor, said valve means having a body portion havingrefrigerant flow pasages therein, a valve member movable to closed andopen positions in said passages for directing refrigerant respectivelyto said restrictor or to said bypass conduit, a device responsive to anincrease in suction pressure beyond a predetermined value for actuatingsaid valve member to its closed position, a presure line connecting saidcircuit from between said evaporator and the inlet of said compressor tosaid device whereby said device is subjected in closing direction ofsaid valve member to the pressure in said circuit between saidevaporator and said compressor inlet, means for moving said valve memberto its open position, and means for applying a restraining force to saidvalve member when said member is in its open position, the force appliedby said last named means being varied in relation to changes in armbient temperature.

4. A valve structure including a valve movable to closed and openposition, means for moving said valve from open position to closedposition, and means for ac. tuating said valve to open positioncomprising an actuating arm biased for movement from a first positlon toa second position, a return arm for returning said actuating arm to itsfirst position, cam means having first and second follower surfaces for,respectively, restraining movement of said actuating armaway from itsfirst position and con trolling movement of said return arm, saidsurfaces said cam means being shaped to effect release in rapidsuccession of said actuating arm and then said return arm whereby saidactuating arm moves from 1ts first po sition to its second position foractuation of said valve and is immediately returned to its firstposition to permit self-actuation of the valve, a toothed ratchet fordriving said cam means and a reciprocating pawl for effectingincremental movement of said ratchet, said ratchet lii b tantiallyuniform tooth configuration except 9 in the region thereof engaged bysaid pawl as said cam means is moved to efiect release of said arms,said region of the ratchet having an oversize tooth thereon foreffecting increased movement of said cam means to insure release of bothof said arms.

5. A se" actuating valve structure for defrostable refrigerator systemscomprising a valve body having refrigerant fiow passages therein, avalve member movable to closed and open positions for controlling flowof refrigerant through said passages, means for moving said member fromits closed position to its open position, a pressure sensitive devicefor moving said member from its open position to its closed position,and a spring detent applying a force to said valve member restrainingmovement thereof in closing direction, said detent comprising abimetallic member which increases its restraining force in response toincrease in ambient temperature.

6. A valve structure comprising a valve body having fluid flow passagestherein, a valve member movable to closed and open positions forcontrolling flow of fiuid through said passage, means for actuating saidvalve member to open position comprising an actuating arm biased formovement from a first position to a second or valve open position, areturn arm for returning said actuating arm to its first position, cammeans, means for driving said cam means, said cam means having first andsecond follower surfaces for, respectively, restraining movement of saidactuating arm from its first position and controlling movement of saidreturn am, said surfaces of said earn means being shaped to effectrelease in rapid succesion of first said actuating arm and then saidreturn arm whereby said actuating arm moves from its first position toits second position for actuation of said valve member to open positionand is thereafter returned by said return arm to its first position topermit closing of the valve member, and means independent of saidactuating means for moving said valve member from open position toclosed position; said valve member when moved to open position by saidactuating member remaining in open position until closed by said lastnamed means.

7. A valve structure including a valve member movable to closed and openpositions, means for actuating said valve to open position including anactuating arm biased for movement from a first position to a second orvalve opening position and a return arm for returning said actuating armto its first position, cam means having first and second followersurfaces for, respectively, restraining movement of said actuating armaway from its first position and controlling movement of said returnarm, said surfaces of said cam means being shaped to effect release inrapid succession of first said actuating arm and then said return armduring one incremental movement of said cam means following a pluralityof preliminary incremental movements of said cam means whereby saidactuating arm moves from its first position to its second position foropening of said valve and is immediately thereafter returned to itsfirst position by said return arm, and means for driving said cam meansfor effecting one incremental movement at a time of said cam meansrepeatedly through said preliminary movements and then said onemovement, said driving means including a movable element and areciprocable pawl for effecting incremental movement of said movableelement, said movable element comprising a series of first members whichare spaced apart to present uniformly spaced drive surfaces to saidpawl, and a second member on said element presenting to said pawl adrive surface which is spaced fro-m the drive surface of the firstmember preceding it, in the direction of movement of said movableelement, a distance greater than the space between the drive surfaces ofsaid first members; the incremental movement of said movable elementeffected by engagement of said pawl with said second membercor-responding to said one incremental movement of said cam means,whereby said cam means is moved a greater incremental distance duringsaid one incremental movement than during said preliminary incrementalmovements.

References (Iited in the file of this patent UNITED STATES PATENTS2,344,215 Soling Mar. 14, 1944 2,666,298 Jones a Jan. 19, 1954 2,717,494Doeg Sept. 13, 1955 2,743,587 Hubacker r May 1, 1956

